Software metrics attempt to quantify the qualitative software quality. A software comlexity measure is one used to capture the programming difficulties during devlopment and predict the maintainability and testability of the software. This paper presents a set of complexity metrics for object-oriented systems based on information flow models and evaluated by means of Weyuker's meta-metrics for their validity. The entities measured by this set of metrics consist of methods, classes, class hierarchies, and programs in an object-oriened system. The attributes of an entity considered are the interactive coupling (external complesity) among entities and the length (internal complexity) of each individual entity. This set of metrics is applied to C++ prrograms.